Nextgen gallery and SEO Yoast plugin xml sitemap

i have two site with Nextgen gallery and WordPress SEO Yoast installed at last upgrade.

in this the sitemap work perfectly https://www.odontotecnico.it/ngg_tag-sitemap.xml

in this i obtain “Not Found- 404 error” https://www.alefoto.it/ngg_tag-sitemap.xml

the other sitemap generated from WordPress SEO Yoast work perfectly for all two sites , only ngg_tag-sitemap.xml for the secon site not work

I tried to disable all Plugin and use twentyeleven theme, but anything !!

have you suggestion for solve ?